88 lines
3.5 KiB
Racket
88 lines
3.5 KiB
Racket
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#lang racket
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(require "../lib.rkt"
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"05.rkt")
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(define input
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(string->program (car (problem-input 7))))
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(define (amplify phase)
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(let*-values ([(_ outA) (exec input #:in (list (first phase) 0))]
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[(_ outB) (exec input #:in (list (second phase) (car outA)))]
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[(_ outC) (exec input #:in (list (third phase) (car outB)))]
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[(_ outD) (exec input #:in (list (fourth phase) (car outC)))]
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[(_ outE) (exec input #:in (list (fifth phase) (car outD)))])
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(car outE)))
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(define part1
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(let ([phases (permutations '(0 1 2 3 4))])
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(apply max (append (map amplify phases)))))
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;; The IntCode interpreter from Day 5, except it uses threads
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(define (exec-pipe program #:ptr [pointer 0] #:thr thread)
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(let* ([instruction (list-ref program pointer)]
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[opcode (remainder instruction 100)]
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[mode1 (remainder (quotient instruction 100) 10)]
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[mode2 (remainder (quotient instruction 1000) 10)]
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[mode3 (remainder (quotient instruction 10000) 10)]
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;; l* : call to get write location from program
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[l1 (λ () (if (zero? mode1) (list-ref program (+ pointer 1)) (+ pointer 1)))]
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[l2 (λ () (if (zero? mode2) (list-ref program (+ pointer 2)) (+ pointer 2)))]
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[l3 (λ () (if (zero? mode3) (list-ref program (+ pointer 3)) (+ pointer 3)))]
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;; v* : call to read values from program
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[v1 (λ () (list-ref program (l1)))]
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[v2 (λ () (list-ref program (l2)))]
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[v3 (λ () (list-ref program (l3)))]
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[next-pointer
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(match opcode
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[(or 1 2 7 8) (+ pointer 4)]
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[(or 3 4) (+ pointer 2)]
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[(or 5 6) (+ pointer 3)]
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[99 (+ pointer 1)])])
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(match opcode
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[(or 1 2)
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(let* ([arith (match opcode [1 +] [2 *])]
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[value (arith (v1) (v2))]
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[program (list-set program (l3) value)])
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(exec-pipe program #:ptr next-pointer #:thr thread))]
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[3
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(let* ([value (thread-receive)]
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[program (list-set program (l1) value)])
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(exec-pipe program #:ptr next-pointer #:thr thread))]
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[4
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(thread-send thread (v1))
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(exec-pipe program #:ptr next-pointer #:thr thread)]
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[(or 5 6)
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(let* ([jump-if (match opcode [5 nzero?] [6 zero?])]
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[next-pointer (if (jump-if (v1)) (v2) next-pointer)])
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(exec-pipe program #:ptr next-pointer #:thr thread))]
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[(or 7 8)
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(let* ([lt-eq (match opcode [7 <] [8 =])]
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[value (if (lt-eq (v1) (v2)) 1 0)]
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[program (list-set program (l3) value)])
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(exec-pipe program #:ptr next-pointer #:thr thread))]
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[99
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(thread-send thread (values program (thread-receive)))])))
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(define (amplify-loop phase)
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(let* ([threadE (thread (exec-pipe input #:thr (current-thread)))]
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[threadD (thread (exec-pipe input #:thr threadE))]
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[threadC (thread (exec-pipe input #:thr threadD))]
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[threadB (thread (exec-pipe input #:thr threadC))]
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[threadA (thread (exec-pipe input #:thr threadB))])
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(thread-send threadE (fifth phase))
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(thread-send threadD (fourth phase))
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(thread-send threadC (third phase))
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(thread-send threadB (second phase))
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(thread-send threadA (first phase))
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(thread-send threadA 0)
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(let loop ()
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(let ([msg (thread-receive)])
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(if (number? msg)
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(begin
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(thread-send threadA msg)
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(loop))
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(let-values ([(_ output) msg])
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output))))))
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(show-solution part1 #f)
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